The objective of this program is to facilitate the management of the NIH Animal Genetic Resource (NIH AGR) through development and utilization of embryo collection, culture, freezing and transplantation as techniques for cryobanking genetic stock and improving reproductive potential. Embryos are frozen slowly in medium containing cryoprotectant to allow sufficient dehydration of embryos to insure post-thaw survival. Following dilution of cryoprotectant after thawing, embryos are cultured to assess in vitro development. Embryos are collected and maintained in a frozen state until needed for rederivation of stocks and strains. This reduces genetic drift and serves to safeguard live colonies from catastrophe. Development of this technology allows banking of embryos for long-term storage and subsequent rederivation under the direction of the Geneticist, SAS. Concurrent comparative research studies are designed to identify modifications in methodology which will enhance female response to ovulation induction regimens and improve post-thaw embryo viability.